IMPORTANCE: Characterizing the quality of supportive cancer care can guide quality improvement. OBJECTIVE: To evaluate nonhospice supportive cancer care comprehensively in a national sample of veterans. DESIGN, SETTING, AND PARTICIPANTS: Using a retrospective cohort study design, we measured evidence-based cancer care processes using previously validated indicators of care quality in patients with advanced cancer, addressing pain, nonpain symptoms, and information and care planning among 719 veterans with a 2008 Veterans Affairs Central Cancer Registry diagnosis of stage IV colorectal (37.0%), pancreatic (29.8%), or lung (33.2%) cancer. MAIN OUTCOMES AND MEASURES: We abstracted medical records from diagnosis for 3 years or until death among eligible veterans (lived ≥ 30 days following diagnosis with ≥ 1 Veterans Affairs hospitalization or ≥ 2 Veterans Affairs outpatient visits). Each indicator identified a clinical scenario and an appropriate action. For each indicator for which a veteran was eligible, we determined whether appropriate care was provided. We also determined patient-level quality overall and by pain, nonpain symptoms, and information and care planning domains. RESULTS: Most veterans were older (mean age, 66.2 years), male (97.2%), and white (74.3%). Eighty-five percent received both inpatient and outpatient care, and 92.5% died. Overall, the 719 veterans triggered a mean of 11.7 quality indicators (range, 1-22) and received a mean 49.5% of appropriate care. Notable gaps in care were that inpatient pain screening was common (96.5%) but lacking for outpatients (58.1%). With opioids, bowel prophylaxis occurred for only 52.2% of outpatients and 70.5% of inpatients. Few patients had a timely dyspnea evaluation (15.8%) or treatment (10.8%). Outpatient assessment of fatigue occurred for 31.3%. Of patients at high risk for diarrhea from chemotherapy, 24.2% were offered appropriate antidiarrheals. Only 17.7% of veterans had goals of care addressed in the month after a diagnosis of advanced cancer, and 63.7% had timely discussion of goals following intensive care unit admission. Most decedents (86.4%) were referred to palliative care or hospice before death. Single- vs multiple-fraction radiotherapy should have been considered in 28 veterans with bone metastasis, but none were offered this option. CONCLUSIONS AND RELEVANCE: These care gaps reflect important targets for improving the patient and family experience of cancer care.